Exception for subtraction fraction

Specification

\[\begin{array}{l} \\ \frac{-\left(f + n\right)}{f - n} \end{array} \]

(FPCore (f n) :precision binary64 (/ (- (+ f n)) (- f n)))

double code(double f, double n) {
	return -(f + n) / (f - n);
}

real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = -(f + n) / (f - n)
end function

public static double code(double f, double n) {
	return -(f + n) / (f - n);
}

def code(f, n):
	return -(f + n) / (f - n)

function code(f, n)
	return Float64(Float64(-Float64(f + n)) / Float64(f - n))
end

function tmp = code(f, n)
	tmp = -(f + n) / (f - n);
end

code[f_, n_] := N[((-N[(f + n), $MachinePrecision]) / N[(f - n), $MachinePrecision]), $MachinePrecision]

\begin{array}{l}

\\
\frac{-\left(f + n\right)}{f - n}
\end{array}

herbie shell --seed 2024238 
(FPCore (f n)
  :name "subtraction fraction"
  :precision binary64
  (/ (- (+ f n)) (- f n)))

Please file a bug report with this information.

error: contract violation expected: string? given: 'neg.f64		L	C
f345	.../match/compiler.rkt	559	40
loop	.../private/map.rkt	40	19
loop	.../private/map.rkt	40	19
loop	.../private/map.rkt	40	19
loop	.../private/map.rkt	40	19
loop	.../private/map.rkt	40	19
compile-expr	/home/nightlies/herbie/bhargav-log-space/src/core/explain.rkt	70	0
explain	/home/nightlies/herbie/bhargav-log-space/src/core/explain.rkt	614	0
explain!	/home/nightlies/herbie/bhargav-log-space/src/core/mainloop.rkt	321	0
run-improve!	/home/nightlies/herbie/bhargav-log-space/src/core/mainloop.rkt	43	0
get-alternatives/report	/home/nightlies/herbie/bhargav-log-space/src/api/sandbox.rkt	184	0
(unnamed)	/home/nightlies/herbie/bhargav-log-space/src/api/sandbox.rkt	280	6
(unnamed)	/usr/local/racket/share/pkgs/profile-lib/main.rkt	40	10
profile-thunk	/usr/local/racket/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/usr/local/racket/collects/racket/engine.rkt	42	24